Rockwell Automation 1746-NR4 SLC RTD/Resistance Input Module User Manual - Manual (Page 136)

Publication 1746-UM008B-EN-P - December 2006
136 Glossary
cut-off frequency
The frequency at which the input signal is attenuated 3 dB by the
digital filter. Frequency components of the input signal below the
cut-off frequency are passed with under 3 dB of attenuation.
data word
A 16-bit integer that represents the value of the analog input channel.
The channel data word is valid only when the channel is enabled and
there are no channel errors. When the channel is disabled, the
channel data word is cleared (0).
dB (decibel)
A logarithmic measure of the ratio of two signal levels.
digital filter
A low-pass noise filter incorporated into the A/D converter. In
addition, the digital filter provides high-rejection notches at
frequencies that are integral multiples of the filter cut-off frequency.
The notches are used for rejecting AC power line noise and higher
frequency noise.
excitation current
A user-selectable current (0.5 mA and 2.0 mA) that the module sends
through the RTD or resistive device to produce an analog signal
which the NR4 can process and convert to temperature or to ohms,
respectively.
effective resolution
The amount of jitter (data variation) that typically occurs in the data
word due to the influence of the internal electrical noise in the
module.
filter frequency
The user-selectable first-notch frequency for the A/D converter’s
digital filter. The digital filter provides AC power line noise rejection
when the first notch is at 10 Hz or at the power line frequency.
full scale error (gain error)
The difference in slope between the actual and ideal potentiometer or
RTD transfer functions.